You are failing to understand how businesses are taxed.
A single member LLC is automatically a disregarded entity. That means you report your income and expenses on a schedule C that is part of your overall tax return form 1040, the same as a sole proprietor with no special legal status.
The alternative choice is to file as an S-corporation. In that case, you file form 1120 for the corporation. The corporation must pay you a salary for the work you do at a fair market wage. That salary is subject to all the usual rules for a salaried employee--you must withhold federal and state income tax, payroll tax, and possibly unemployment and workers comp. You must issue yourself a W-2, and file quarterly payroll form 941. If you have profits in excess of a fair salary for your work, you can take that as a profit distribution. To file your LLC as an S-corp, you must send the IRS a special form, and the decision can't be more than 60 days retroactive, so if you have income from more than 60 days ago, you would have to file as both a disregarded entity and an S-corp. (Or, you could make the S-corp election to be effective January 1, and then file as a disregarded entity this year and as an S-corp in the future.). However, filing as an S-corp is substantially different than filing as a disregarded entity/sole prop., and you should not do this without significant expert advance planning and advice.
Now back to your tax return, if you file as a sole prop/disregarded entity, you and the business are one in the same. You may use either your SSN or your EIN. If you have an EIN, I would use it, since the whole point of getting an EIN is to avoid giving out your personal SSN. (If you have other employees, you must use your EIN.). You are also not required to have separate business bank accounts, although it is a very good idea to do so since it makes record keeping somewhat easier.
